Dunham explained that she had to get the dog retrained as the Los Angeles facility, called Zen Dog, due to Lamby’s aggressive nature.

“When I met him I knew we'd have an amazing journey. But his aggression - which was unpredictable- and his particular issues, which remain myriad, weren't manageable, at least not by me. I did what I thought the best mother would do, which was to give him a life that provided for his specific needs,” she wrote in a lengthy Instagram post.

Dunham tweeted that Lamby "suffered terrible abuse as a pup that made having him in a typical home environment dangerous."

She says Lamby was so aggressive he once bit her on the behind, after which she posted an image of her bloody underwear. The Girls creator called giving up Lamby "one of the toughest decisions" of her life.

Dunham adopted Lamby at a shelter in Brooklyn, N.Y., in 2013. Officials are now insisting there is no evidence Lamby had been abused prior to his adoption.

In fact, Lamby had shown no signs of being aggressive to humans or other dogs previously, the shelter said.

“It's come to my attention that the staff at the shelter where I adopted Lamby have a very different account of his early life and behavioral issues than I do. While I'm sorry to have disappointed them, I can't apologize,” Dunham wrote on Instagram.

Trainer Matt Beisner took care of Lamby when he ended up at Zen Dog.

"She and I had conversations about how she was going to be perceived publicly, knowing she was going to do what was best for the dog and that it was not going to go over very well. She was willing to do that,” he said.

Zen Dog says Dunham did the right thing by bringing the dog there. They have since adopted Lamby out to a new home.